Certain machine tools such as plate mills operate on a workpiece with the pallet oriented in the vertical position. If the workpiece is large, mounting the workpiece on the pallet with the pallet in the vertical position can be a difficult task. The workpiece has to be supported against the force of gravity while it is being clamped to the pallet. Additionally, when the pallet is in a vertical position, it may be physically difficult to reach the top of the pallet in order to align the workpiece along the top edge of the pallet and to actuate the clamps along the top of the pallet to secure the workpiece to the pallet.